1.This movie is a watered down version of the famous book.

这部电影是那本名著的删减版。

water down:

(idiomatic) To simplify or oversimplify; to make easier; to make less difficult.

2.The action movie looks like it's nothing but eye candy.

动作片像是华而不实的东西。

Most of the images on the website are not more than eye candy.

网页上大多数图片虽然吸引眼球，却毫无意义。

eye candy:

(US, idiomatic) Any object or sight with considerable visual appeal.

3.The critics damned the new film with faint praise although it's really popular recently.

虽然这部电影最近广受欢迎，评论家们却明褒实贬。

damn with faint praise:

(idiomatic) To provide praise that is minimal or inconsequential, implying that such praise is the best that could be said.